Twitter bots 🤖 scan the entire Twitter ecosystem 24/7 to flag spammers, trolls, and the accounts acting against Twitter's policies. Occasionally, these bots wrongly flag genuine user accounts. When Twitter locks an account, there might be a couple of reasons;
The most common reason is having no phone number connected to your account. If you don't have a phone number linked to your account, most likely, the bots will flag the account as it is not genuine, sooner or later.
The second common reason is that your account might be locked for security purposes by Twitter. If you are logged in to your account and see a message that your account has been locked for security purposes, this means that Twitter have detected suspicious behavior and bots thought that your Twitter account might be compromised. You need to follow Twitter instructions to re-activate your account. When you do that, you prove you're willingly using 3rd party Apps.
Your account is limited because it may have violated the Twitter Rules If your account is limited because it may have violated the Twitter Rules, Twitter may ask you to perform specific actions before they remove your restricted state. These actions may include verifying your email address, adding a phone number to your account, or removing Tweets that violate Twitter rules.
Twitter uses some automated systems to understand if you willingly started to use 3rd party applications like Circleboom, Buffer, Hootsuite, etc. by locking out you instead of just asking if you began to use these apps willingly. When you open up the Twitter application on your phone, it automatically verifies you by sending an email or a text message. After that, you're good to go.
It happens when Twitter locks you out. In that case, users can see your profile and your Tweets as the account is still active. When you verify your account, the numbers on your Twitter account will automatically be reinstated by Twitter (This is not a thing 3rd party applications like Circleboom able to do.) Don't forget to add your mobile phone numbers to your Twitter accounts to prevent future lock-outs.